Structural phase transitions, dehydration and decomposition of ammonium hypodiphosphates.

IF 1.3 3区化学 Q3 CHEMISTRY, MULTIDISCIPLINARY

Acta crystallographica Section B, Structural science, crystal engineering and materials Pub Date : 2025-08-01 Epub Date: 2025-07-03 DOI:10.1107/S2052520625004408

Katarzyna A Ślepokura, Paulina Kurowska, Daria Budzikur-Maciąg, Vasyl Kinzhybalo

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Abstract

The ferroelectric diammonium hypodiphosphate, (NH₄)₂(H₂P₂O₆) (3), is the only known so far ammonium salt of hypodiphosphoric acid, H₄P₂O₆. A series of seven new ammonium salts is reported: triclinic (P1) (1) and monoclinic (C2/c) (2) polymorphs of monoammonium (NH₄)(H₃P₂O₆), isostructural (NH₄)₅(H₂P₂O₆)(HP₂O₆)·H₂O (4) and (NH₄)₃(HP₂O₆) (5), and tetraammonium (NH₄)₄(P₂O₆) (6), (NH₄)₄(P₂O₆)·H₂O (7) and (NH₄)₄(P₂O₆)·2H₂O (8). Monoammonium hypodiphosphates 1 and 2 crystallize in perovskite-type structures. Form 1 undergoes an order-disorder phase transition related to the dynamics of ammonium cations, the unit-cell doubling and no change in space group type. Dehydration-decomposition of 4 leads to the equimolar mixture of 3 and 5, whereas dehydration of dihydrate 8 proceeds in two steps, resulting in the formation of monohydrate 7 and then anhydrate 6. Compound 7 undergoes a reversible phase transition (P2₁/c ↔ C2/c) concerned with the reorganization of the hydrogen-bond network. Thermal analysis (DSC and TG-DTA) and variable-temperature microsample powder X-ray diffraction were used to analyse the phase transitions, dehydration and decomposition processes.

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次二磷酸铵的结构相变、脱水和分解。

铁电性的次二磷酸二铵（NH4）2(H2P2O6)(3)是目前已知的唯一的次二磷酸铵盐。报道了7种新型铵盐：单铵（NH4）（H3P2O6）三斜晶型（P1）(1)和单斜晶型（C2/c）(2)多晶型（NH4）5(H2P2O6)（HP2O6）·H2O(4)和（NH4）3(HP2O6)(5)，四铵（NH4）4(P2O6) (6), (NH4)4（P2O6）·H2O(7)和（NH4）4（P2O6）·2H2O(8)。次二磷酸一铵1和二铵2结晶为钙钛矿型结构。形式1经历了与铵离子动力学相关的有序-无序相变，单位胞加倍，空间基团类型没有变化。4的脱水分解得到3和5的等摩尔混合物，而二水化合物8的脱水分两步进行，形成一水化合物7和无水化合物6。化合物7经历一个与氢键网络重组有关的可逆相变（P21/c↔C2/c）。热分析（DSC和TG-DTA）和变温微粉x射线衍射分析了相变、脱水和分解过程。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Acta crystallographica Section B, Structural science, crystal engineering and materials CHEMISTRY, MULTIDISCIPLINARYCRYSTALLOGRAPH-CRYSTALLOGRAPHY

CiteScore

3.60

自引率

5.30%

发文量

期刊介绍： Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published.